its regarding Virgin Hub 3.0

Hi i noticed a while back when i had a couple of relatives visiting me that when my router exceeds 11 connections across 2.4ghz and 5ghz the Wi-Fi just dies like it reboots itself, that goes on endlessly until you turn off Wi-Fi on one of the devices so it can reconnect. It does not matter if the devices use internet or just locally connected smart device. if i have 2 phones 3 Light bulbs 2 Smart appliances 1 Laptop 1 Tablet 1 Fire stick and a Printer then i got to turn off one of them or put air plane mode on phone or tablet so the wifi works normaly. Those lights are cheap ASDA smart from TCP so they only work via 2,4ghz Complained to the Virgin Media and they see no problem and if i want to try to resolve something i have to call Technical help provider ...... Or shed some money for a Gigabit Router with better WIFI than HUb3 got. What would you do .